1/*	$NetBSD: readpass.c,v 1.2 2009/06/07 22:38:47 christos Exp $	*/
2/* $OpenBSD: readpass.c,v 1.48 2010/12/15 00:49:27 djm Exp $ */
3/*
4 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include "includes.h"
28__RCSID("$NetBSD: readpass.c,v 1.2 2009/06/07 22:38:47 christos Exp $");
29#include <sys/types.h>
30#include <sys/wait.h>
31
32#include <errno.h>
33#include <fcntl.h>
34#include <paths.h>
35#include <readpassphrase.h>
36#include <signal.h>
37#include <stdarg.h>
38#include <stdio.h>
39#include <stdlib.h>
40#include <string.h>
41#include <unistd.h>
42
43#include "xmalloc.h"
44#include "misc.h"
45#include "pathnames.h"
46#include "log.h"
47#include "ssh.h"
48#include "uidswap.h"
49
50static char *
51ssh_askpass(const char *askpass, const char *msg)
52{
53	pid_t pid, ret;
54	size_t len;
55	char *pass;
56	int p[2], status;
57	char buf[1024];
58	void (*osigchld)(int);
59
60	if (fflush(stdout) != 0)
61		error("ssh_askpass: fflush: %s", strerror(errno));
62	if (askpass == NULL)
63		fatal("internal error: askpass undefined");
64	if (pipe(p) < 0) {
65		error("ssh_askpass: pipe: %s", strerror(errno));
66		return NULL;
67	}
68	osigchld = signal(SIGCHLD, SIG_DFL);
69	if ((pid = fork()) < 0) {
70		error("ssh_askpass: fork: %s", strerror(errno));
71		signal(SIGCHLD, osigchld);
72		return NULL;
73	}
74	if (pid == 0) {
75		permanently_drop_suid(getuid());
76		close(p[0]);
77		if (dup2(p[1], STDOUT_FILENO) < 0)
78			fatal("ssh_askpass: dup2: %s", strerror(errno));
79		execlp(askpass, askpass, msg, (char *) 0);
80		fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno));
81	}
82	close(p[1]);
83
84	len = 0;
85	do {
86		ssize_t r = read(p[0], buf + len, sizeof(buf) - 1 - len);
87
88		if (r == -1 && errno == EINTR)
89			continue;
90		if (r <= 0)
91			break;
92		len += r;
93	} while (sizeof(buf) - 1 - len > 0);
94	buf[len] = '\0';
95
96	close(p[0]);
97	while ((ret = waitpid(pid, &status, 0)) < 0)
98		if (errno != EINTR)
99			break;
100	signal(SIGCHLD, osigchld);
101	if (ret == -1 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
102		memset(buf, 0, sizeof(buf));
103		return NULL;
104	}
105
106	buf[strcspn(buf, "\r\n")] = '\0';
107	pass = xstrdup(buf);
108	memset(buf, 0, sizeof(buf));
109	return pass;
110}
111
112/*
113 * Reads a passphrase from /dev/tty with echo turned off/on.  Returns the
114 * passphrase (allocated with xmalloc).  Exits if EOF is encountered. If
115 * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no
116 * tty is available
117 */
118char *
119read_passphrase(const char *prompt, int flags)
120{
121	const char *askpass = NULL;
122	char *ret, buf[1024];
123	int rppflags, use_askpass = 0, ttyfd;
124
125	rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
126	if (flags & RP_USE_ASKPASS)
127		use_askpass = 1;
128	else if (flags & RP_ALLOW_STDIN) {
129		if (!isatty(STDIN_FILENO)) {
130			debug("read_passphrase: stdin is not a tty");
131			use_askpass = 1;
132		}
133	} else {
134		rppflags |= RPP_REQUIRE_TTY;
135		ttyfd = open(_PATH_TTY, O_RDWR);
136		if (ttyfd >= 0)
137			close(ttyfd);
138		else {
139			debug("read_passphrase: can't open %s: %s", _PATH_TTY,
140			    strerror(errno));
141			use_askpass = 1;
142		}
143	}
144
145	if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL)
146		return (flags & RP_ALLOW_EOF) ? NULL : xstrdup("");
147
148	if (use_askpass && getenv("DISPLAY")) {
149		if (getenv(SSH_ASKPASS_ENV))
150			askpass = getenv(SSH_ASKPASS_ENV);
151		else
152			askpass = _PATH_SSH_ASKPASS_DEFAULT;
153		if ((ret = ssh_askpass(askpass, prompt)) == NULL)
154			if (!(flags & RP_ALLOW_EOF))
155				return xstrdup("");
156		return ret;
157	}
158
159	if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) {
160		if (flags & RP_ALLOW_EOF)
161			return NULL;
162		return xstrdup("");
163	}
164
165	ret = xstrdup(buf);
166	memset(buf, 'x', sizeof buf);
167	return ret;
168}
169
170int
171ask_permission(const char *fmt, ...)
172{
173	va_list args;
174	char *p, prompt[1024];
175	int allowed = 0;
176
177	va_start(args, fmt);
178	vsnprintf(prompt, sizeof(prompt), fmt, args);
179	va_end(args);
180
181	p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF);
182	if (p != NULL) {
183		/*
184		 * Accept empty responses and responses consisting
185		 * of the word "yes" as affirmative.
186		 */
187		if (*p == '\0' || *p == '\n' ||
188		    strcasecmp(p, "yes") == 0)
189			allowed = 1;
190		xfree(p);
191	}
192
193	return (allowed);
194}
195